The present invention relates to an improved system for mounting a tool element subassembly to the output spindle of a power tool and more particularly to a coupling flange that is adapted to accommodate and drivingly engage both hubbed and non-hubbed types of abrasive disc subassemblies which may be mounted to the spindle of a portable grinder.
The abrasive disc subassembly used on portable grinders generally consists of an abrasive disc that is carried by an internally threaded collar. The collar is adapted to be mounted to the externally threaded spindle of the grinder. Typically, the direction of rotation of spindle when the motor in the grinder is energized is such that the collar will self-thread onto the spindle and bear against an annular shoulder formed on the spindle. Alternatively, it has been proposed to provide an annular composite "soft" washer assembly between the collar on the abrasive disc subassembly and the annular shoulder on the spindle to prevent the collar from becoming locked or jammed against the annular shoulder of the subassembly. This latter type of mounting construction is described in U.S. Pat. No. 4,449,329, issued May 22, 1984, for a "Composite Washer Assembly", and assigned to the assignee of the present invention. A further type of mounting construction employs a supporting flange member that is positioned against the annular shoulder of the spindle and at its radial distal end supports and rotationally drives the abrasive disc.
In addition, a new mounting assembly for hubbed abrasive disc subassemblies has recently been proposed that comprises an abrasive disc having permanently attached to its backside a first metal backing flange or "hub". A second base flange member is positioned on the spindle of the grinder against the annular shoulder of the spindle. The base flange member has a pair of radially spaced annular drive surfaces on one side that are adapted to engage corresponding radially spaced raised annular contact surfaces on the backing flange or hub of the abrasive disc subassembly. The other side of the base flange member is adapted to engage and be driven by the annular shoulder on the spindle of the grinder or by a "soft" washer assembly of the aforementioned type disposed between the base flange member and the annular shoulder of the spindle.
Although this latter two-component system for driving grinding wheels provides operational advantages over the previously employed systems, it possesses the disadvantage of being incompatible with prior designed non-hub-type abrasive disc subassemblies, which are most commonly available. Specifically, a portable grinder equipped with the base flange member of the aforementioned two-component system will not drive a conventionally designed abrasive disc subassembly not having the proper backing flange. Rather, in order to use a conventional non-hub abrasive disc subassembly, the base flange member must first be removed from the spindle of the grinder and replaced with a conventional support flange member. This, of course, is undesirable not only from a convenience standpoint, but also because the base flange member, once removed, is likely to be lost or misplaced, particularly in a commercial environment where portable grinders are most frequently used.
Accordingly, it is the primary object of the present invention to provide an improved drive system for mounting a tool element and, in particular, an abrasive disc subassembly, to the output spindle of a power tool such as a portable grinder.
In addition, it is an object of the present invention to provide an improved mounting and drive assembly that is completely compatible with the abrasive disc subassemblies for the newer two-component mounting system as well as with the conventionally designed non-hub-type abrasive disc subassemblies.